Mushroom Cultivation Techniques

by Randy McLaughlin

The cultivation of edible mushrooms can be a rewarding profession or hobby.

Growing mushrooms can be done as a pastime or professionally. Techniques for cultivating shiitake, oyster, button and straw mushrooms are well known, but several different methods provide good yields. Some mushrooms are more simple and quicker to grow for the hobbyist, such as the paddy straw mushroom and the oyster mushroom. The choice of mushroom to grow often depends what is available as a growing substrate.

Shiitake Mushroom Cultivation

Shiitake mushrooms (Lentinula edodes) are grown on healthy hardwood logs of many species. Logs must be soaked or already moist, from 3-5 inches in diameter and around 3 1/2 feet long. Many holes are drilled for inoculum along the length of the log at a predetermined spacing. Sawdust inoculum is introduced into these holes to a depth of 1 inch. Soft wax is used to seal the hole, and it is also used to seal the log ends during dry seasons. Logs are stacked diagonally on a support or in triangles and then covered to help maintain humidity. During a 2-month period, they are inspected twice for growth and potential contamination by the green Trichoderma fungus. Spawn growth is evident by the appearance of white thread-like growth (mycelium) around inoculation sites and at the end of the logs. During this time, keeping the logs moist is important if the climate is dry. Fruiting is forced by soaking the logs. The logs are ready when they show significant spawn run throughout and at the log ends. As the logs dry afterward, fruiting will begin.

Oyster Mushroom Cultivation

In nature, oyster mushrooms (Pleurotis ostreatus) grow from fallen trees. They can be grown in the same manner as the shiitake, but spawn can be introduced in different ways, including cutting an inch slice off the end of the log and then nailing it back on after inoculating the cut end. Inoculated logs are placed in black polyethylene bags containing wet sand or vermiculite, and then placed in a cool area. Fruiting begins about a month later. Commercial production of this fungus uses substrates like chopped wheat straw, cottonseed hulls, sawdust, composted straw or mixtures. Ground limestone is added at 1 percent weight/weight to some substrates to adjust the pH. These substrates are pasteurized before inoculum is introduced. Inoculum is added at from 1.5 to 5 percent of the substrate weight. The inoculated substrate can be placed in beds, plastic bags, trays or bottles. Production time is similar to that with logs.

Button Mushroom Cultivation

The Button Mushroom (Agaricus bisporus) is grown on a wide variety of composts, including those made with horse or chicken manure and plant wastes like wheat straw and corn cobs. Mushroom spawn is added to the pasteurized compost at around 1 pound per square yard of bed area (160 pounds of substrate). Once the fungus colonizes the compost, with 50 percent of the surface area showing white mycelium, the substrate is cased (topped) with a mixture of lime and peat (pH of 7-7.5). Mushroom spawn is sometimes added to the casing to increase yield. Thereafter, it takes a week to 10 days for the fungus to start pinning, or producing mushroom fruiting body precursors. Reducing the incubation temperature to 60 degrees F from the incubation temperature of 75 degrees helps initiate production. In a week to 10 days after pinning, mature mushroom buttons appear.

Cultivating the Paddy Straw Mushroom

If you eat Chinese food, then you may be familiar with the straw mushroom (Volvariella volvacea). It can be grown easily if you have access to rice straw or dried banana leaves. Both materials are used to make 3-inch diameter, 18-inch long bundles that are wrapped in 2 percent urea-soaked newspaper. The spawn is applied to the middle of the bundle and the bundles are stacked four high in a row that can extend up to 12 feet long. For each row, 8 ounces of spawn are used to inoculate the substrate. The row doesn't need watering during the rainy season. During dry seasons, watering begins a week after setting the beds, and daily afterwards until pins (mushroom precursors) form. Harvest begins 10-14 days later can continue for a month. More than 25 pounds of mushrooms can be harvested from a single bed. Composts made with the rice straw and chicken manure work as alternative substrates, but pasteurization is required. This method is not commonly used in rural areas.

About the Author

As a scientist, Randy McLaughlin has been a professional technical writer since 1980. He has a Master of Science from Texas A&M University and a Ph.D. in plant pathology from the University of Wisconsin. McLaughlin covers diverse topics, including Costa Rica, technical guides, alternative healing and spiritual development.

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